Evolution and Classification of land plants
Definition: Multicellular eukaryotic autotroph
With cell walls made of cellulose
1.Phylum Algae: (used to be part of kingdom Plantae
Now it is considered part of kingdom Protozoa)
- Lives in marine or aquatic environments
- Uses diffusion for gas exchange, to absorb
- It uses swimming sperm and non motile eggs for
a. Examples: Green algae, Red algae, Brown algae.
2. Phylum Bryophyta – land plants which are very delicate
They have no cuticle (protective waxy covering)
- They use diffusion for gas exchange
- Use swimming sperm and they have eggs
- They have gametophytes, which are separate sexes
They have male and female gametophytes.
Sperm swim from males to females.
Examples: 1. Moss
3. Phylum Tracheophyta – land plants which have some of the following
- Have a cuticle
- Have vascular tissue (conducting tubes which can deliver minerals,
- Have stomata – “breathing holes” for gas exchange
- Are much bigger than bryophytes
- Examples are
- 1. Subphylum Pterophyta – All ferns.
2. Subphylum Sphenophyta – Horsetails.
FERNS AND HORSETAILS HAVE SWIMMING SPERM
3. Subphylum Spermophyta – All plants which make seeds
including trees of all kinds and including flowering plants.
SPERMOPHYTA DO NOT HAVE SWIMMING SPERM.
THEY MADE AN INNOVATION IN EVOLUTION: POLLEN
THEY DO NOT rely on water for SEXUAL REPRODUCTION.
- They all have vascular tissue – some extend quite high up. Tall trees
- All have cuticle, stomata.
- A. “GYMNOSPERM GROUP” -
- 1. CLASS GINGKOAE – ginko
- 2. CLASS CONIFERAE – all evergreen trees
- 3. CLASS ANGIOSPERMAE – all plants that are deciduous trees, AND ALL
- FLOWERING PLANTS.
THREE EVOLUTIONARY TRENDS
1. EARLY PLANTS need water to sexually reproduce, LATER PLANTS DON’TSEXUAL REPRODUCTION REQUIRED sperm and egg in early plants. Later plants used pollen, using wind. And the most recent plants use vector pollination.
ALTERNATION OF GENERATION
plants alternate between two generations. It is as if they use a different body form every other generation. For example, a male gametophyte mates with a female gametophyte and they create their offspring, a sporophyte. Then the sporophyte makes the next generation, gametophytes.
Imagine if you looked exactly like your grandparent and your child looked exactly like your parent